I. Field of the Invention
This invention relates to a portable microcomputer system and in particular to a battery operated microcomputer system having a hard disk.
II. Description of the Related Art
The development of low power consumption CMOS LSIs has led to the development of powerful battery operated microcomputer systems. In the past, non-volatile data storage for such computers has been provided by microcassette data storage devices. As data storage technology has advanced, some battery operated computer systems have incorporated floppy disk devices (FDD) and hard disk devices (HDD). These peripheral data storage devices consist of a rotating magnetic storage medium driven by an electric motor. Since floppy disks spin at a low speed, the disk is rotated only when necessary to read or write data; however, the high rotating speeds of hard disks and the low required access times require that the HDD be kept rotating continuously. This results in high power consumption and low battery life in a battery powered computer system, and the battery life is determined mostly by the power consumption of the HDD.
In conventional battery powered computer systems, the charge, or energy, state of the battery is monitored during computer system operation. When the battery energy state has dropped to a predetermined level, normally measured by battery voltage, a visual or audible alarm is triggered giving the operator an opportunity to either store data currently in RAM and shut down the system or plug in an external power adapter to support continued computer system operation.
Battery powered computer systems employing HDDs experience a sharp drop in battery charge in a relatively short time, which is particularly acute in systems employing Ni-Cd battery power sources. Ni-Cd batteries maintain a fairly constant voltage during a discharge cycle until a low energy state is reached, then the voltage drops rapidly leaving only a very short time for the operator to take action to prevent a data loss, especially when a high power consumption peripheral device such as an HDD is in use. If the operator does not act quickly enough, valuable data will be lost as the battery rapidly expends its energy by continuing to operate the HDD.
It is an object of the present invention to minimize the risk of data loss in a battery powered computer system having a high power consumption peripheral device such as an HDD when the battery system reaches the end of a discharge cycle.
It is a further object of the present invention to shut down a high power consumption peripheral device such a HDD in a battery powered computer system only when the HDD is in a standby mode and not actively reading or writing data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.